Hi, as a med student at UT Southwestern (btw, this is not UT Dallas- you might offend someone) I can tell you this much. Medicine here is very strong. It's considered one of the top in the country. The people who built the department established a resident-driven patient care program with quite a bit of didactic conferences.
The reason some think it's a malignant program is that there is a very large patient load. This may be bad if you are seeking a more low-key program, but it's good if you want a tonn of experience with a very good diversity of pathology. Medicine docs graduating from UT Southwestern are generally considered very experienced and competent.
Overall, if you want to get a great education and are willing to work for it, this is a great program. If you are (like myself) want a bit less work, this may not be a program for you.
As far as competitiveness. It's one of the more competitive in the country. From what I've heard top quarter and with good (well above the mean) board scores.
I interviewed at UTSW. Very strong program which attracts perhaps a more cutthroat type, although there are always exceptions. The faculty do stand out, although I question how much you actually see of the faculty whose names are thrown around so frequently. One weakness I did notice was a lack of any appreciable outpatient medicine in the first year. Personally, I am not heading for a career in outpatient medicine, but it really is a vital component of medical training.
As for cases, like any metropolitan area, they are bound to get a wide variety. But in reality, most large metropolitan areas with a public hospital will have their share of zebras. Its hard to list this as a strength, when most true academic medicine programs in large cities, with public/county hospital affiliation, get good cases.
My impression of the residency's opinion of itself, was perhaps a bit inflated. A majority of the residents were from Texas or the south, with a fair amount of inbreeding, with a number of UTSW grads sticking around. The program does attract those interested in academic careers, which may add to its perceived strength.
Ultimately, I chose not to go to UTSW because of the extreme case load. Capping out on call nights was fairly common according to residents I talked to. Seeing patients is a good thing, but having so many that you have such little time to think...may be bad... for some. However, program choice really is dependent on your personality and the preferred personality of those you work with....be it malignant, or not.